1. Field of the Invention
The present invention relates to devices for crawling through pipes. More particularly, the present invention relates to a pipe crawler having the flexibility necessary to efficiently negotiate bends in piping systems.
2. Discussion of Background
Although vehicles for moving through piping systems have been known for some time, significant drawbacks continue to exist with such pipe crawlers. Namely, current pipe crawlers have difficulty negotiating non-linear segments of piping within the piping systems.
Typically, pipe crawlers comprise a front leg assembly, a rear leg assembly and an extendible body connecting the two leg assemblies. The leg assemblies and body cooperate to move in an "inchworm"-like manner through piping. When the legs of the rear leg assembly extend to engage the inner wall of the piping, the front legs can retract and be moved by extending the body forward through the piping. Then the front legs can extend to engage the wall of the pipe so that the rear legs can retract and the body retract, allowing the rear leg assembly to be pulled toward the front leg assembly. This "inchworm" type of motion allows the pipe crawler to progress through piping systems that are, for the most part, linear.
For example, U.S. Pat. No. 5,121,694 issued June 1992 to the author of the device described herein and commonly assigned, describes such a pipe crawler. Additionally, a patent application with Ser. No. 730,425, filed July 1991 by Hapstack, describes an instrumentation carriage adaptable for use with U.S. Pat. No. 5,121,694. Although the means for connecting the pipe crawler in U.S. Pat. No. 5,121,694 and the Ser. No. 730,425 instrumentation carriage exhibits some flexibility, neither device alone has the requisite degree of flexibility for efficiently negotiating non-linear segments of piping.
Other pipe crawlers exist that also have varying degrees of flexibility, yet none is believed to be effective for moving through non-linear piping segments, that is, around pipe elbows, bends and the like. For instance, Negishi, in U.S. Pat. Nos. 5,080,020 and 4,938,081, alternately forces pressurized fluid into and out of an elastic, contractible body to advance the device along tubular or columnar members having linear and non-linear segments.
Similarly, Collingwood, in U.S. Pat. No. 4,285,242, and Braithwaite, in U.S. Pat. No. 4,285,242, disclose pipe inspection vehicles having flexible joints mounted within the body of the vehicle. However, both Collingwood and Braithwaite use the joints to restrain movement, rather than to provide flexibility for the vehicles.
Despite the well known existence of pipe crawling devices, there still remains a need for pipe crawlers that can better negotiate non-linear segments of piping systems.